Globular clusters can be used to determine the absolute luminosity of the tip of the red giant branch (TRGB), which in turn can be used to measure the distance to nearby galaxies.
Using Gaia EDR3 parallaxes,
[1]} recently derived a distance of \(5.24 \pm 0.11\)  kpc to \(\omega \)  Cen. Using this distance, they derived an absolute I-band magnitude of the
TRGB of \(M_{I,TRGB}=-3.97 \pm 0.06\) , from which they deduced a value of the local Hubble constant of \(H_0=71.2 \pm 2.0\)  km/sec. In contrast, [2]} used stars in the LMC to derive
an an absolute TRGB magnitude of \(M_{I,TRGB}=-4.05 \pm 0.06\) , using eclipsing binaries in 47 Tuc and the SMC to calibrate the LMC distance.
